799 research outputs found

    Odnos između strukturnih i funkcionalnih promena kod primarnog glaukoma otvorenog ugla

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    EXAMPLES OF LCA METHODOLOGY IMPLEMENTATION IN STEEL INDUSTRY

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    Steel industry kept pace with actual trends for environmental protection in many ways – through different technological improvements considering environment protection, important share of recycling in the steel production, design of so called “eco-steels”, materials designed according to recent environmental directives and legislatives, etc. In the frame of steel production monitoring, LCA methodology is very important for obtaining an accurate environmental picture of a process, due to the fact that the process should be evaluated over its entire life cycle. A number of tools and methodologies have been developed in recent years to assess the potential environmental impacts associated with a product, process or activity during its entire life cycle. The examples of Life Cycle Assessment (LCA) are used by large steel industrial companies as potentially helpful tool for improving the production processes, efficiency of resource utilization and significantly reduction of waste generation and emissions are presented in this paper

    Kalorimetrijsko ispitivanje tekućih Ga-Me (Sn, Zn) legura Oelsenovom metodom

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    The results of calorimetric investigation of binary, liquid Ga-Me (Sn, Zn) alloys are presented in this paper. According to constructed space enthalpy diagram and enthalpy isotherm diagram, activities, activity coefficients and other partial and integral molar quantities were determined at different temperatures. Also, comparison was made with existing literature data

    Electrical Characterization and Impedance Response of Lanthanum Doped Barium Titanate Ceramics

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    The dielectric permittivity and dissipation factor of La-doped and undoped BaTiO3 were investigated as a function of frequency and temperature. The impedance response was used to study the electrical properties of La-doped BaTiO3 over the temperature range from room temperature (RT) to 350 degrees C. La-doped and undoped BaTiO3, obtained by a modified Pechini method, were sintered in air at 1300 degrees C for 2 and 16 hours. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE). The most suitable electrical circuit for the interpretation of experimental results is found to be the equivalent circuit consisting of resistors and CPE elements which replace the capacitor elements. The contribution of grain boundary resistance to the total resistance of a system is remarkable at low temperature. Dielectric permittivity of doped BaTiO3 was in the range of 8000 to 12000 at 1 kHz and the dissipation factor was less than 1%

    Dilatometer Investigations of Reactive Sintering of Zinc Titanate Ceramics

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    Poster presented at the The Sixth Yugoslav Materials Research Society Conference - YUCOMAT 2004, Herceg Novi, Crna Gora, September 13-17, 2004

    Chemical risk factors responsible for the formation of wedge-shaped lesions

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    Introduction: Non-carious tooth substances loss pose a major health problem of a modern man. The literature often collectively describes all non-carious lesions and is therefore difficult to compare results obtained by different authors. Chemical factors are one of the predisposing factors responsible for the formation of wedge-shaped erosions. Aim: Examination of chemical risk factors as one of the predisposing causes responsible for the formation of wedge-shaped lesions. Method: We examined 62 patients with wedge-shaped erosions (mean age 45.52 ± 12.03 years, 58.1% of men) and 60 patients without erosions in the control group (mean age 34.40 ± 9.28 years, 60% men) . The entire examination was completed by using a questionnaire at the Dental Clinic of the University of Pristina - Kosovska Mitrovica. salivary pH was measured by the pH meter. Results: The results show that the wedge-shaped lesions often occur equally in both men and women. Considerably often it might appear in older people but can also occur in teenagers. Patients with wedge-shaped erosion have increased acidity of saliva, a heightened sense of acid in the mouth and consume a lot more carbonated drinks compared to patients without erosions. Conclusion: Wedge-shaped lesions are more common in people older than 40 years. Taking into account the results obtained in this study it can be concluded that the chemical risk factors truly fall within the predisposing factors that may be responsible for the creation of wedge-shaped erosions

    Thermal analysis and kinetics of the chalcopyrite-pyrite concentrate oxidation process

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    The paper presents the results of experimental investigation of the chalcopyrite-pyrite concentrate oxidation in the air. Characterisation of the initial sample and oxidation products was done by ICP-AES, XRD, EDXRF methods. Phase stability diagrams were constructed for Cu-Fe-S-O system at 25, 450, 650 and 900 °C. Equilibrium composition of the charge for the optimal oxidation process was calculated. DTA-TG analysis was used for monitoring the oxidation process. Kinetic parameters in non-isothermal conditions were determined, based on Kissinger and Ozawa methods.Values of activation energies showed that all stages of the oxidation process occur in the kinetic field

    Synthesis of BaTiO3 from a mechanically activated BaCO3-TiO2 system

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    In this article the solid state reaction of BaTiO3 formation from a mechanically activated BaCO3-TiO2 system has been investigated. An equimolar mixture of BaCO3 and TiO2 powders was activated in a planetary ball mill in a continual regime for 0, 30 and 90 min, pressed and thermally treated up to 1200°C. The effect of the milling and firing regime on the phase formation was investigated by the X-ray diffraction (XRD) method and differential thermal analysis (DTA). Deconvolution of the experimental DTA curve corresponding to the BaTiO3 synthesis process has been performed. The influence of the activation time on the change of characteristic temperature for each elementary step in the complete solid-state reaction of BaTiO3 formation, was analyzed. These results were correlated with the ones obtained by SEM characterization and by XRD analysis.U ovome radu je analiziran uticaj mehaničke aktivacije sistema BaCO3- TiO2 na formiranje BaTiO3. Ekvimolarne smeše praha BaCO3 i TiO2 su aktivirane u planetarnom mlinu u kontinualnom režimu tokom 0, 30 i 90 min. Uzorci su zatim presovani i termički tretirani do 1200oC. Efekat mlevenja i zagrevanja na promene faza je analiziran primenom rendgenske fazne analize i diferencijalne termijske analize. Izvršena je dekonvolucija eksperimentalno dobijene DTA krive koja odgovara procesu sinteze BaTiO3, kao i analiza uticaja vremena aktivacije na promene karakteristične temperature za svaki pojedinačni elementarni proces tokom sinteze barijum titanata. Ovi rezultati su korelisani sa rezultatima dobijenim SEM i XRD analizom

    Riparijalne oblasti kao koridori invazije Xanthium strumarium u Srbiji

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    Xanthium strumarium L., also known as common cocklebur, is a potentially invasive weed species in Serbia. It is one of the most competitive weeds, strongly affecting the yield of some crops, such as maize, soybean, sunflower, sugar beet, etc. Since watercourses act as important transportation routes for the long-distance dispersal of weeds and the fruit of X. strumarium is easily dispersed by water, our aim was to analyse the degree of X. strumarium invasion in riparian areas of Serbia and examine the role of rivers and canals as its potential invasion corridors. The field research was carried out during the summer months of 2013,2014, and 2015, along the course of 35 rivers and five major canals of the Danube- Tisa-Danube Hydrosystem (HSDTD) in Serbia. Fieldwork was conducted along 100 m long transects of 500 m long river stretches (chosen following the RHS methodology), where the invasive alien weed species presence and abundance were recorded. Over the period of three years, the presence of X. strumarium was recorded along the course of 33 rivers (94.25%), while it was documented along 66.85% of the total number of river stretches. However, along the canals, it was recorded in only 12% of the localities. The data on the distribution ofX. strumarium expand the existing knowledge on the distribution of this economically harmful weed species in our country, while at the same time highlighting riparian areas of rivers as potentially important corridors of its spread.Xanthium strumarium L. u narodu poznat kao obična ili zelena boca, je potencijalno invazivna korovska vrsta na području Srbije. Jedna je od najkompetitivnijih korovskih vrsta, koja jako utiče na prinos nekih kultura, kao što su kukuruz, soja, suncokret, repa, itd. Imajući u vidu činjenicu da vodotokovi predstavljaju značajne transportne puteve za disperziju korovskih vrsta na veće razdaljine, naš cilj je bio da analiziramo stepen invazije X. strumarium u riparijalnim područjima Srbije i ispitamo kakva je uloga reka i kanala kao njegovih potencijalnih koridora invazije. Terenska istraživanja obavljena su u periodu letnjih meseci 2013, 2014. i 2015. godine, duž toka 35 reka i pet glavnih kanala hidrosistema Dunav-Tisa-Dunav u Srbiji. Istraživanja su vršena na 100m dugim transektima u okviru 500 m dugih deonica rečnog toka (odabranih u skladu sa RHS metodologijom), gde su beleženi prisustvo i pokrovnost stranih invazivnih biljnih vrsta. Tokom trogodišnjeg perioda istraživanja, prisustvo X. strumarium zabeleženo je duž toka 33 reke (94,25%), a duž 66,85% od ukupnog broja rečnih deonica. Međutim, duž toka kanala, ova potencijalno invazivna vrsta registrovana je na samo 12% lokaliteta. Podaci o rasprostranjenju vrste X. strumarium proširuju postojeće znanje o rasprostranjenju ove ekonomski značajne korovske vrste u našoj zemlji, dok u isto vreme ističu riparijalne oblasti reka kao potencijalno značajne koridore njenog širenja
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